The present disclosure relates to a vehicle-mounted communication system.
Control systems that use multiple control devices, with each control device carrying out control based on computer programs (called simply “programs” hereinafter), are used in a variety of fields. In the field of automobile control, vehicles are provided with many ECUs (Electronic Control Units) serving as control devices, with the ECUs configured to exchange information over a vehicle-mounted LAN (Local Area Network) and carry out a variety of processes in cooperation and in tandem with each other.
For example, JP 2014-193654A describes a vehicle-mounted gateway that stores a routing map necessary for determining a relay destination for information, and that relays the information among a plurality of in-vehicle networks. In JP 2014-193654A, the in-vehicle networks communicate according to the CAN (Controller Area Network) communication standard, but the networks connected to the gateway also include networks that communicate according to another communication standard, such as Ethernet (registered trademark).
PLC (power line communication), in which communication signals are superposed over positive and negative power supply lines for supplying power, is sometimes used between control devices inside the vehicle and control devices outside the vehicle. For example, JP 2013-187968A discloses a charging communication ECU that uses power line communication to exchange data necessary for charging with a charging device located outside of the vehicle. The charging communication ECU is also connected to a vehicle-mounted communication network (in-vehicle network), but the power line communication terminates at the charging communication ECU and is thus clearly separated from communication among the ECUs.
With communication using an in-vehicle network, the vehicle body is normally used as a return path, and harnesses including the power supply lines are run vertically and horizontally throughout the vehicle. Compared to the weight of the vehicle body, the weight of these harnesses is not light enough to be ignored. Moreover, there tends to be an increase in power supply noise, voltage drops, and power loss as more power is consumed by vehicle-mounted devices. In response to this, Anette Sedlmaier, Michael Wortberg, Stefan Lobmeyer, and Karl Ring. “ATZ elektronik worldwide,” Ausgabe, Issue 5, 2014, p. 52-56 proposes a centralized power supply architecture that uses a multi-drop connection for the power supply lines, from the engine compartment in the forward part of the vehicle body, to the rear part of the vehicle body.